A very good comment on, "What Separates a Generalist and a Dabbler?" by Patri Friedman -
I think looking at accomplishment is a good angle, but there is more to it than just the choice of whether to ship. There is also whether you even get something ship-worthy made. Some people are able to create useful or complete things in new fields quickly, for a variety of reasons. Most people are not.
Good strategy here is very important – identifying low hanging fruit, picking projects big enough to be useful but small enough to complete, which use your relative strengths in the field. Identifying the summary that needs writing, the experiment that needs doing, the other field that hasn’t heard about this one but would benefit from it. Someone good at this will contribute more with the same amount of learning.
That whole comment is brilliant. Re-read it if you're skimming.
Identify low-hanging fruit, work on those, and that will aid in making something ship-worthy. Very good stuff.
Patri's blog is here - http://patrissimo.livejournal.com/ - I find his newest entry, "Annual Review process," to be particularly valuable and timely - recommended.